1. Parameters with Eco-performance of Solar Powered Wireless Sensor Network
Hung-Chi Chu (1)1, Fang-Lin Chao (2)1 and Wei-Tsung Siao(3)1
1 Chaoyang University of Technology, Taichung, Taiwan, R.O.C

2. Green wireless sensor network development platform2

3. Wireless Sensor Node

4. Routing WSN
energy-saving data gathered technology 4

5. TECHNOLOGY Solar powered Wireless Sensor Network
Solar panel and LCA data
Charging circuit
Battery and environment

6. Solar panel and LCA data
Amorphous silicon, the process step is simpler than mono-crystalline cell, therefore the panel requires less energy consumptions in production phase [7].
Mono-crystalline silicate cells have the highest energy conversion efficiency of 14 percent, but it requires the most energy to produce.
emits 55 grams of global warming pollutant per kilowatt-hour

7. carbon emission's point of view
solar powered systems are 90 to 300 times lower than those from coal powered plants [8].
This is caused by a two times higher solar cell conversion efficiency for m-Si modules
compensates the two 2 times higher energy requirement during manufacture.

8. Charging circuit
The solar energy to battery charge conversion efficiency reached 14.5%
PV system efficiency of nearly 15%, and a battery charging efficiency of approximately 100%.
Directly charging the battery from the PV system with no intervening electronics
matching the PV maximum power point voltage to the battery charging voltage

9. Battery and environment
Lithium-ion batteries is strongly temperature- dependent.
operating at high temperatures can result in the destruction of the cell.
higher temperatures.
Unless heat is removed faster than it is generated, it possible causes thermal runaway [11].
The battery thermal management system must be designed keep the cell operating within its sweet spot
avoid premature wear out of the cells.
The cycle life quoted in specification assumes operating at room temperature.

10. GREEN DESIGN CONSIDERATIONS

11. GREEN DESIGN CONSIDERATIONS

12. The scenarios
individual Circuit move to PCB factory PCB surface mount process Node Chassis assembly Distributed to sale point Network node placement Node connecting testing and trouble shooting Node take back during maintains

13. Green wireless sensor node13

14. Green wireless sensor node

15. Spec. of wireless node (MCU) MCU clock 24.5MHz FLASH ROM 64K RAM 4K
Radio freq
frequency
2.4 GHz
Max data rate
250kpbs
Transmit distance
100m
RF channel
16 (5MHz)
Power
Trans/Receive
29mA/27mA
Sleep
4uA
Working conditions
Supply V
Temperature °C
Humidity %

16. Re-charging battery NOKIA Li-ion battery iNeno Ni-MH battery， 3.7 (V)
capacity 1020mAh。
iNeno Ni-MH battery，
9 (V)
Capacity 300mAh。

17. Charging performance (outdoors: 40000-80000 Lux)
Initial
2.6V 6V
30 minute
3.6V
3.2V 3V 9V
60 minute
3.7V
3.4V
9.2V
90 minute
3.8V
9.4V
120 minute
150 minute

18. WSN and panel chosen

19. With three solar panels in series, it produces electricity for 5. 8V-6
With three solar panels in series, it produces electricity for 5.8V-6.4V and charging current 80mA-235mA.
The battery voltage increase rapidly as the ambient light intensity increased.
Normally the charging process reaches 95% of capacity within two hour period of time.

20. Measurement
For long term evaluation of system performance, Onset HOBO U12 standalone data loggers were utilized.
12-bit resolution for detecting data, direct USB interface

21. Charging voltage measurement during 12 hours (light intensity, battery voltage, temperature)

22. Reliability issues
Temperature
Panel
voltage
26℃
7.50Ｖ
5.45Ｖ
28℃
7.28Ｖ
5.35Ｖ
30℃
7.17Ｖ
5.30Ｖ
32℃
7.20Ｖ
5.22Ｖ
34℃
7.23Ｖ
5.16Ｖ
36℃
7.25Ｖ
5.09Ｖ
38℃
7.22Ｖ
5.03Ｖ
40℃
7.19Ｖ
4.97Ｖ
solar panel power output voltage, between 26 and 40 degrees there was a drop in power output from a peak of 7.5V down to 7.19V
maintaining a lower temperature, the system failure rate will decrease and output power can also be increased.

23. Solar Panel Configurations
Once installed people can not easily change the reception angle
Based on the situations of surrounding environment and the sunshine conditions, the actual installation maybe varied.

24. Measurement of penel temperature
Configuration
Temperature
(a)-c
42.3
(b)-c
37.8
(a)-i
39.4
(b)-i
37.3
Highest temperature is configuration (a)-c, therefore it needs more open space to improve convection
Reduce the heat transfer from structure.

25. Measured panel temperature while outdoor light intensity changed Ta 30 ° C)

26. Maintenance issue
The PV panel has an expected life cycle of 20 years, but without routine maintenance the panel may fail after 10 years.
The battery has an expected life cycle of 4 years, but this can be reduced to a range of 1 years.
charge controller can last 5 years, depending on the level of misuse.
The highest rate of equipment failure occurs with the battery is most often the result of battery misuse.

27. Conclusions
By constantly monitoring the voltage level and smart routing protocol, the WSN with solar gives lower maintenance cost.
The network can monitor the status of each node periodically to detect that if a WSN node fails or is defective.
Through the integration of wireless sensor network technologies and solar charging system, the development of low power and long lasting networks can be achieved.
Eco-design parameters can be compared from both cost and system maintenance in early development phase.